1. Field of the Invention
This invention relates to a process for the preparation of alkylene glycols by catalytic hydration of the corresponding alkylene oxide.
2. Description of the Prior Art
The production of alkylene glycols from alkylene oxides is known and is practiced commercially. Of particular interest is the production of ethylene glycol from ethylene oxide. The thermal hydration of ethylene oxide in water produces monoethylene glycol (MEG) which is used as a base material in the production of poly(ethylene terephalate) or PET which can be used to make polyester fibers, resins, films and bottles. MEG is also as a major active component in antifreeze.
Hydration of ethylene oxide can be through catalytic and non-catalytic means. Non-catalytic hydration of ethylene oxide to MEG requires a large excess of water to inhibit the formation of diethylene glycol (DEG) and other higher glycols. Even with a large excess of water the molar selectivity to MEG is only about 88%. In addition, the water must be distilled from the glycol to obtain a high purity product. Distillation is a very energy intensive process.
Catalytic hydration of ethylene oxide may use smaller amounts of water and can be carried out at lower temperatures and pressures. There are numerous examples of catalysts for hydration of an alkylene oxide to alkylene glycol.
U.S. Pat. No. 5,260,495 discloses a process for producing monoalkylene glycol with a metalate-substituted hydrotalcite composition in which an anionic clay of metal oxide/hydroxide layers with large organic anion interstitial spacers has some of these spacers replaced with a metalate anion.
U.S. Pat. No. 5,874,653 discloses a process for preparing an alkylene glycol by reaction alkylene oxide with water in the presence of a catalyst of a polymeric organosiloxane ammonium salt as an ion exchange resin catalyst.
U.S. Pat. No. 4,967,018 discloses a process for catalytic hydrolysis or alkylene oxide to alkylene glycol with a mixed metal framework catalyst of a divalent metal cation, such as magnesium, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, palladium, platinum, copper, zinc, cadmium, mercury, tin and lead; a trivalent metal cation, such as aluminum, antimony, titanium, scandium, bismuth, vanadium, yttrium, chromium, iron, manganese, cobalt, ruthenium, nickel, gold, gallium, thallium and cerium; and an anion, such as halide, nitrite, nitrate, sulfite, sulfate, sulfonate, carbonate, chromate, cyanate, phosphite, phosphate, molybdocyanate, bicarbonate, hydroxide, arsenate, chlorate, ferrocyanide, borate, cyanide, cyanaurate, cyanaurite, ferricyanide, selenate, tellurate, bisulfate, oxalate, acetate, hexanoate, sebacate, formate, benzoate, malonate, lactate, oleate, salicylate, stearate, citrate, tartrate and maleate.
U.S. Pat. No. 5,488,184 discloses a process for preparation of alkylene glycols by reacting an alkylene oxide with water in the presence of a catalyst of a solid material having electropositive sites, such as silica, silica-alumina, clay, zeolite and ion-exchange resin, coordinated with an anion, such as bicarbonate, bisulfite, phosphate and carboxylate.
U.S. Pat. No. 6,187,972 discloses a process for producing an alkylene glycol from an alkylene oxide and carbon dioxide via the intermediate formation of ethylene carbonate with a catalyst of an alkali metal bromide or iodide, an alkaline earth metal bromide or iodide, an ammonium halide, such as tributyl methylammonium iodide, or a phosphonium halide, such as tributylmethylphosphonium iodide.
U.S. Pat. No. 4,307,256 discloses a process for producing alkylene glycols from alkylene oxides, water and carbon dioxide in the presence of an organic base catalyst, such as triethylamine, dimethylaniline and pyridine.
An acceptable hydration catalyst would have high selectivity to the monoalkylene glycol and a decrease in the amount of water required in comparison with a non-catalytic process. However, prior art catalysts can have problems which make their use disadvantageous. Soluble acid catalysts have corrosion problems. Alkaline catalysts have lower selectivity to MEG. Alkali metal or ammonium halides have lower solubility and are likely to precipitate which causes scaling and corrosion problems. Amine-based catalyst can have a strong, undesirable odor which can cause quality problems with the product. Ion exchange resins can result in metallate salts in the glycol product or can require long residence times. The ion exchange resins may also swell during the reaction and have limited tolerance to heat.
Ordinary Lewis acid catalysts are water sensitive and can be hydrolyzed by water. However, some Lewis acids, such as rare earth (lanthanide) triflates, are water tolerant and can be used in a variety of chemical reactions.
Indium triflate is used with lithium perchlorate in the catalytic acylation of aromatics to aromatic ketones (“Indium triflate: An Efficient Catalyst for the Friedel-Crafts Acylation of Aromatics”, Christopher G. Frost and Joseph P. Hartley, Fourth International Electronic Conference on Synthetic Organic Chemistry (ECSOC-4), Aug. 3, 2000).
Bismuth triflate is used for acylation of aromatics and alcohols and the sulphonation of aromatics (“Bismuth(III) Chloride and Triflate—Novel Catalysts for Arylation and Sulphonation Reactions—Review”, Le Roux C et al, SynLett, 2002, 181).
U.S. Pat. No. 6,444,857 discloses reacting an alcohol with a diol derivative in the presence of an acid catalyst, such as scandium triflate, to form an intermediate in a process for producing Vitamin A.
U.S. Pat. No. 6,362,375 discloses metal triflate catalysts to catalyze a reaction between carboxylic acid and an aromatic in the presence of a volatile organic compound which forms an azeotrope with water, such as toluene, to produce aryl ketones.
U.S. Pat. No. 6,352,954 discloses a Lewis acid, such as scandium triflate, encapsulated in a network of polymer gel which can be used in a variety of organic syntheses, such as imino-aldo condensation, Mannich-type reactions, Michael reactions and Friedel-crafts reactions.
U.S. Pat. No. 6,348,631 discloses acylation or sulphonation of aromatics to aromatic ketones or sulphones with a Lewis acid, such as a rare earth triflate.
U.S. Pat. No. 6,194,580 discloses forming esters of tertiary alcohols by reacting a compound containing a tertiary alcohol with a acyl heteroaromatic ion-based compound in the presence of a lanthanide metal based catalyst such as scandium triflate.
U.S. Pat. No. 6,111,135 discloses reacting ethylene, paraformaldehyde, formic acid and scandium triflate to form 1,3 propanediol diformate ester.
U.S. Pat. No. 6,040,484 discloses hydroxylation of phenolic compounds with hydrogen peroxide with scandium triflate.
U.S. Pat. No. 5,990,264 discloses copolymerization of tetrahydrofuran with cyclic carboxylic anhydride with scandium triflate.
U.S. Pat. No. 5,948,696 discloses an aldol reaction of treating a resin-bound aldehyde or its imine with silyl enol ether in the presence of scandium triflate in dichloromethane.
U.S. Pat. No. 5,770,678 discloses polymerization of cyclic ether, such as tetrahydrofuran, using metal compounds, such as scandium triflate and acetyl chloride or acetic anhydride.
U.S. Pat. No. 5,728,901 discloses a process for nitrating an arene with nitric acid in the presence of a catalyst, such as scandium triflate.
U.S. Pat. No. 4,543,430 discloses a process for the preparation of addition products of epoxides and hydroxylated compounds in the presence of a catalyst of a salt of trifluoromethanesulfphonic acid, such as a triflate of an alkali (Group I) metal, an alkaline earth (Group II) metal or heavy metal. The examples used aluminum triflate as the preferred catalyst. Lithium triflate was also disclosed as a catalyst.
It would be advantageous to have a catalyst for hydration of an alkylene oxide to the corresponding alkylene glycol without the disadvantages of prior art catalysts.